The invention relates to a fluorescence-emitting light source unit that excites a phosphor with use of excitation light to cause the phosphor to emit fluorescence.
A fluorescence-emitting light source unit is known, as a green-light light source used for a projector for example, in which a phosphor is irradiated with laser light serving as excitation light to cause the phosphor to emit green light as fluorescence. As one example of such a fluorescence-emitting light source unit, Japanese Unexamined Patent Application Publication No. 2011-13316 discloses a fluorescence-emitting light source unit that includes a wavelength conversion member in which a surface of a rotary wheel is coated with a phosphor. In the fluorescence-emitting light source unit disclosed in JP2011-13316A, the wavelength conversion member is irradiated with laser light in a blue region to cause the phosphor in the wavelength conversion member to generate light in a green region.
As another example of such a fluorescence-emitting light source unit, Japanese Unexamined Patent Application Publication No. 2011-198560 discloses a fluorescence-emitting light source unit that includes a wavelength conversion member as illustrated in FIG. 10. The wavelength conversion member includes a fluorescent member 41 made of a YAG sintered material and disposed on a surface of a substrate 42 via a barium sulfate layer 43. The substrate 42 is made of an AlN sintered material and provided with a heat sink fin 45 on a back surface thereof. In the fluorescence-emitting light source unit disclosed in JP2011-198560A, the fluorescent member 41 in the wavelength conversion member is irradiated with laser light in a blue region serving as excitation light to generate light in a green region at the fluorescent member 41.
Japanese Unexamined Patent Application Publication No. 2012-109400 proposes to form a corrugated structure on a surface that serves as an excitation light receiving surface of a wavelength conversion member in a fluorescence-emitting light source unit. The corrugated structure suppresses reflection of excitation light at the excitation light receiving surface. More specifically, JP2012-109400A discloses the fluorescence-emitting light source unit provided with the wavelength conversion member in which a translucent substrate is disposed on a fluorescent member. The translucent substrate has the corrugated structure including projections that are arrayed on a surface thereof, and the surface of the translucent substrate serves as the excitation light receiving surface. In the fluorescence-emitting light source unit disclosed in JP2012-109400A, the fluorescent member has a configuration in which a phosphor is dispersed in a sealant. The sealant is made of a glass material such as inorganic glass, or a resin material such as a silicone resin. The translucent substrate is made of a material having high heat conductivity, such as sapphire.